If they have been vomiting, i would say it narrows it down to internal parasites. including worms and protozoal infections. They are highly contagious.
symptoms include
wieght loss - tick
lethargy - tick
listlessness - tick
discoloured urates with red tinges - unknown
lack of appetite - tick
regurgitation - tick
bloating of abdomen - unknown
diarrhoea - unknown
constipation - unknown
faecal matter stuck to cloaca - unknown
try and answer the unknowns
definately need a reasonably fresh stool sample taken to the vet in a ziplock bag, labled with details and kept under room conditions
its going to be a long hard road